docs: def zero_datetime(dt, tz=None):
      """
      Return the given datetime with hour/minutes/seconds/ms zeroed and the
      timezone coerced to the given ``tz`` (or UTC if none is given).
      """
      if tz is None:
          tz = get_current_timezone()
      return coerce_naive(dt).replace(hour=0, minute=0, second=0, microsecond=0)